The powerful typhoon, packing wind gusts of 126 kph with an atmospheric pressure of 970 hectopascals at its center, was about 330 kilometers southwest of Jeju traveling at a speed of 20 kph as of 6 a.m., according to the Korea Meteorological Administration (KMA).

The typhoon is expected to pass about 130 km southeast of Jeju around noon and 170 km southwest of the southeastern city of Busan at around 6 p.m. The closest point the typhoon is expected to be to Jeju is forecast to be around 3 p.m., while it is expected to be closest to Busan around 10 p.m.

The interior and safety ministry upgraded the weather alert level to "vigilance" from "attention" Saturday as the typhoon is expected to seriously affect the country's southern region.

The KMA warned that strong winds and heavy downpours are expected to hit Jeju Island, parts of the southern areas and the country's easternmost islets of Dokdo.

"There is a need to thoroughly brace for the typhoon in coastal and inland areas as serious damage is expected," a weather agency official said.

According to the transport ministry, 489 flights were expected to be canceled across South Korea on Sunday due to the typhoon, beginning with Asiana Airlines Flight OZ8900 scheduled to depart from the southern island of Jeju for Seoul's Gimpo at 6:30 a.m.

More cancellations are expected later in the day as the typhoon approached the country, the ministry said.

"Passengers are advised to make sure their flights remain on schedule before leaving for airports," a transport ministry official said.